One of the problems associated with relay multiplexing of low level analog signals is that the capacitance from the relay contacts to the coils tends to degrade the AC common mode rejection of the multiplexer. In a typical multi-channel prior art relay multiplexer, each channel has high and low signal input lines and a guard line. Normally the contacts of the relay are electrostatically shielded from the relay coil. The function of the guard line is to provide an electrostatic shield for the high and low signal inputs. When the electrostatic shield is driven by the guard, the effective capacitance between the relay contacts and associated coil is minimized. However, in spite of the electrostatic shield, the capacitance of a typical relay from the open contact to the coil may be as much as 2 picofarads and the capacitance from the closed contacts to the coil may be as much as 4 picofarads. Also, in the conventional case, the ground at the signal source and the ground at the relay multiplexer may be separated by some distance and therefore there may be an AC difference in potential between the two grounds due to magnetically induced voltages or ground current flow. This difference in ground potentials is normally referred to as a common mode signal. This invention provides a means for nullifying the effect of the capacitance between each coil and its associated relay contacts.